Light-emitting device and method for producing same

ABSTRACT

There is provided a light emitting device highly resistant to the environment, and having good heat resistance, light resistance and gas barrier property, and a method for producing same. With the light emitting device, a substrate  2  and interconnect patterns  5 A,  5 B formed on the surface thereof are covered with an acrylic resin primer  10  having better gas barrier property than a silicone resin sealing resin part  3.  Light resistance is ensured by the silicone resin sealing resin portion  3  and the gas barrier property can be ensured by the acrylic resin primer  10.

TECHNICAL FIELD

The present invention relates to a light emitting device, as well as amethod for producing the same, on which an LED (Light Emitting Diode)chip is mounted.

BACKGROUND ART

In 1990's, blue LEDs were developed and marketed, and white LEDs incombination with YAG (yttrium-aluminum-garnet) fluorophor that emitsyellow light at high efficiency upon reception of light from the blueLED chip were also developed. In response to this, development directedtoward stabler chromaticity of white color or higher brightness has beenbeing advanced in view of applications and progresses for generallighting using LEDs and backlight light sources of LEDs for TV use. Alarge challenge in making such development is to improve the thermalresistance and light resistance of the sealing resin for sealing the LEDchip.

White LEDs have a problem of deterioration of peripheral members due toblue light, which is emitted from the LED chip in use and which is shortin wavelength and large in energy. When epoxy resin is used as thesealing resin, there occur such deteriorations as discoloring of thesealing resin due to the short wavelength and large energy of theemission of the LED chip, so that high-brightness light emission cannotbe maintained for long time. As sealing resins that can meet the desirefor that long-time high-brightness light emission, silicone-based resinshave been being in use.

However, silicone-based resins, although excellent in light resistance,are poor at gas barrier property in not a few cases. Poor gas barrierproperty of the sealing resin causes occurrence of condensations at theinterface between the sealing resin and the substrate or package due topermeation of steam as an example, leading to deteriorations orshort-circuits of interconnect patterns or chip electrodes. Also, whilesealing resins for vehicle use need to have corrosive-gas resistance,poor gas barrier property of the sealing resin causes occurrence ofdeteriorations or short-circuits of the interconnect patterns or chipelectrodes, as in the case of condensations, making it impossible tosatisfy the reliability.

Meanwhile, some silicone-based resins are denatured with resins of goodgas barrier property, but those are lowered in light resistance. Underthe current circumstances, it is quite difficult to find out an optimumsealing resin.

Besides, since silicone-based resins are so weak in adhesion that heatgeneration of the chip or the like causes resin peeling to occur atinterfaces with peripheral members due to differences in coefficient ofthermal expansion. This leads to characteristic deteriorations as alight emitting device such as degradation of light-emission brightness.

Thus, as it stands, even adopting silicone-based resins can hardly meetthe desires for thermal resistance, light resistance and gas barrierproperty.

In this connection, Patent Literature 1 (JP 2004-339450 A) discloses anLED package for improving the light resistance of the sealing resin.This LED package, including an opening portion composed of a bottom faceand a side wall, is integrally formed from formation resin so that thebottom face of the opening portion has end portions of a positiveexternal electrode and a negative external electrode exposed withspecified distances, respectively. It is also described that in this LEDpackage, a primer layer is provided on the LED package surface beforeproviding mold resin (sealing resin). Further, in this LED package, usedas the primer layer are primer compositions characterized by includingacrylic polymers, silanol condensation catalysts, silane coupling agentand/or epoxy group-containing compounds as an essential component in asolution. As a result of this, peeling after the light resistance testis suppressed, and the bonding reliability between the LED package andthe sealing resin is improved.

In the prior art shown above, although improvement of the adhesionproperty during the thermal resistance test and the light resistancetest by the primer layer is fulfilled, yet improvement of the gasbarrier property is not disclosed.

CITATION LIST Patent Literature

PATENT LITERATURE 1: JP 2004-339450 A

SUMMARY OF INVENTION Technical Problem

Accordingly, an object of the present invention is to provide a lightemitting device, as well as a method for producing the same, which ishigh in thermal resistance, light resistance and gas barrier propertyand high in environment resistance.

Solution to Problem

In order to achieve the above object, there is provided a light emittingdevice comprising:

a substrate;

a metal portion formed on a surface of the substrate;

an LED chip mounted on the substrate;

a primer made of resin which covers at least part of the metal portion;and

a sealing resin portion which covers the LED chip and at least part ofthe primer to seal the LED chip, wherein

the primer is made from a resin which is higher in gas barrier propertythan the sealing resin portion.

According to the light emitting device of this invention, since theprimer made of a resin higher in gas barrier property than the sealingresin portion covers the metal portion formed on the surface of thesubstrate, the gas barrier property can be improved.

In an embodiment, the primer is formed into a layer shape.

According to the light emitting device of this embodiment, the gasbarrier property can be improved securely with the layered primer.

In an embodiment, the primer is made from an acrylic resin.

According to the light emitting device of this embodiment, the gasbarrier property can particularly be improved.

In an embodiment, the metal portion includes an interconnect pattern.

According to the light emitting device of this embodiment, the gasbarrier property for the interconnect patterns formed on the substratesurface can be improved.

In an embodiment, the metal portion includes a lead frame.

According to the light emitting device of this embodiment, the gasbarrier property for the lead frame can be improved.

In an embodiment, the metal portion includes a metal reflection coating.

According to the light emitting device of this embodiment, the gasbarrier property for the metal reflection coating can be improved.

In an embodiment, a surface of the metal portion is made from Ag, orAgBi-based alloy, or AgNd-based alloy, or an Ag alloy containing 0.5 to5.0 wt % of at least one kind of metal selected from Pt, Au, Cu, Pd, Mg,Ti and Ta.

According to the light emitting device of this embodiment, aparticularly effective gas barrier property for the surface of the metalportion containing silver, which is indeed high in reflectivity butliable to blackening, can be provided with protection by the primer.

In an embodiment, the substrate is made from any one of alight-reflective resin, metal and ceramic.

According to the light emitting device of this embodiment, since lightirradiated from the LED chip is reflected by the substrate, lightemitted from the LED chip can be blocked from being attenuated.

In an embodiment, at least a top face of the LED chip is exposed fromthe primer made of resin.

According to the light emitting device of this embodiment, since the topface of the chip, which becomes higher in temperature, is exposed fromthe resin-made primer, influences of heat on the primer can be reduced.

In an embodiment, the LED chip has its top face and side face coatedwith the primer made of resin.

According to the light emitting device of this embodiment, the primerapplying step becomes simple to achieve, allowing a spin coat process orother processes to be selected in addition to dispensing process, whichgives an advantage for an easier achievement of cost reduction.

In an embodiment, the primer covers a top face of the substrate.

In an embodiment, the primer covers an entire surface of the substrate.

In an embodiment, the primer covers a top face of the substrate, and theLED chip is mounted on the primer covering the top face of thesubstrate.

According to the light emitting device of this embodiment, the lightemitting device is suitable for cases in which electrodes are providedon the top face of the substrate. In this case, forming the primerbefore die bonding or wire bonding allows the primer application to bedone by brush, roller or the like, so that the primer can be formed moresimply. In addition, in cases where the primer is applied over theentire surface of the substrate, dipping process or the like can also beselected for the formation of the primer, allowing further costreduction and higher throughput to be realized.

In an embodiment, the metal reflection coating is formed on thesubstrate,

the primer is formed on the metal reflection coating, and

the interconnect pattern is formed on the primer.

According to the light emitting device of this embodiment, a gas barrierfor the metal reflection coating can be fulfilled by the primer.

In an embodiment, the primer has a thickness of 0.01 μm to 100 μm.

According to the light emitting device of this embodiment, gas barrierproperty of the primer can be ensured, and decreases of brightness dueto optical losses caused by discoloration (yellowing) with heat or lightcan be reduced. It is noted that when the thickness of the primer isless than 0.01 μm, there can occur an abrupt increase in gas permeationamount due to coating irregularities or the like. Further, when thethickness of the primer is over 100 μm, there occurs decreases of thebrightness due to optical losses caused by discoloration (yellowing)with heat or light.

In an embodiment, the sealing resin portion is in close contact with asurface of at least part of the primer.

In an embodiment, the LED chip is placed within a recess portion of thesubstrate,

the primer covers a bottom face of the recess portion of the substrate,

the sealing resin portion is in close contact with the surface of theprimer and seals the LED chip, and

the primer is not exposed.

According to the light emitting device of this embodiment, the sealingresin for sealing the LED chip is in close contact with the surface ofthe primer that covers the bottom face of the recess portion of thesubstrate. Therefore, when gas contained in the sealing resin is bledout, the gas can be allowed to escape upward without obstruction of theprimer. In addition, in a case where the primer is formed on the sealingresin, when gas contained in the sealing resin is bled out, there is noescape place, causing a possibility that the primer may be damaged.

In an embodiment, the sealing resin portion is made from silicone resin.

According to the light emitting device of this embodiment, the lightresistance can be improved by the sealing resin made from siliconeresin.

In an embodiment, the sealing resin portion contains a fluorophor.

According to the light emitting device of this embodiment, wavelengthconversion of light can be done by the fluorophor to emit fluorescentlight.

In an embodiment, a refractive index of the sealing resin portion and arefractive index of the primer, both being within a range of 1.2 to 1.8,are generally equal to each other.

According to the light emitting device of this embodiment, since therefractive index of the sealing resin portion and the refractive indexof the primer are generally equal to each other, optical losses due tothe total reflection at the interface between the sealing resin and theprimer can be eliminated.

In an embodiment, the light emitting device comprises a reflector whichis placed around the LED chip and which reflects light emitted by theLED chip.

According to the light emitting device of this embodiment, since lightfrom the LED chip is reflected by the reflector, the light attention canbe suppressed.

In an embodiment, the reflector and the substrate are made from oneidentical base material.

According to the light emitting device of this embodiment, the reflectorcan be made with simplicity.

In an embodiment, a surface of the reflector is made from Ag, orAgBi-based alloy, or AgNd-based alloy, or an Ag alloy containing 0.5 to5.0 wt % of at least one kind of metal selected from Pt, Au, Cu, Pd, Mg,Ti and Ta.

In an embodiment, the primer covers the surface of the reflector.

According to this embodiment, although the surface of the reflectorcontains silver that is high in reflectivity but liable to blackening,yet the protection with the primer makes it possible to provide aneffective gas barrier.

In an embodiment, a method for producing the light emitting devicecomprises the step of:

applying the primer onto the surface of the reflector before placing thereflector around the LED chip.

According to this embodiment, the primer can easily be applied uniformlyon the surface of the reflector.

There is provided a method for producing a light emitting device,comprising the steps of:

applying a resin-made primer onto a substrate in which a metal portionis formed on its surface and on which an LED chip is mounted so that theresin-made primer covers at least part of the metal portion; and

coating the LED chip and at least part of the resin-made primer with asealing resin and curing the sealing resin, thereby forming a sealingresin portion, wherein

the primer is made from a resin higher in gas barrier property than thesealing resin portion.

According to the production method of this embodiment, at least part ofthe metal portion formed on the surface of the substrate is covered withthe primer made from a resin higher in gas barrier property than thesealing resin portion. Therefore, the gas barrier property can beimproved.

In an embodiment, the light emitting device is mounted onto a printedboard onto which a primer made from a resin material identical to thatof the primer has been applied.

According to the mounting method of this embodiment, a light emittingdevice having a good gas barrier property can be mounted on a printedboard having a good gas barrier property.

In an embodiment, a coefficient of thermal expansion of the sealingresin portion and a coefficient of thermal expansion of the primer aregenerally equal to each other.

According to the light emitting device of this embodiment, impairment ofthe close contact between the sealing resin and the primer due toinfluences of heat can be avoided.

Advantageous Effects of Invention

According to the light emitting device of this invention, the LED chipand the primer are sealed with the sealing resin, and moreover theprimer, which is made from a resin higher in gas barrier property thanthe sealing resin portion, covers the metal portion formed on thesurface of the substrate. Thus, the gas barrier property can be improvedeven under heat- or light-susceptible environments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view showing a main-part constructionof a light emitting device according to a first embodiment of thepresent invention;

FIG. 2A is a schematic sectional view for explaining production processof the light emitting device according to the first embodiment;

FIG. 2B is a schematic sectional view for explaining production processof the light emitting device according to the first embodiment;

FIG. 2C is a schematic sectional view for explaining production processof the light emitting device according to the first embodiment;

FIG. 2D is a schematic sectional view for explaining production processof the light emitting device according to the first embodiment;

FIG. 2E is a schematic sectional view for explaining production processof the light emitting device according to the first embodiment;

FIG. 3A is a longitudinal sectional view showing a main-partconstruction of a light emitting device according to a second embodimentof the invention;

FIG. 3B is a longitudinal sectional view showing a modification of thelight emitting device according to the second embodiment;

FIG. 4A is a longitudinal sectional view showing a main-partconstruction of a light emitting device according to a third embodimentof the invention;

FIG. 4B is a longitudinal sectional view showing a modification of thelight emitting device according to the third embodiment;

FIG. 5A is a longitudinal sectional view showing a main-partconstruction of a light emitting device according to a fourth embodimentof the invention;

FIG. 5B is a longitudinal sectional view showing a modification of thelight emitting device according to the fourth embodiment;

FIG. 6 is a longitudinal sectional view showing a main-part constructionof a light emitting device according to a fifth embodiment of theinvention;

DESCRIPTION OF EMBODIMENTS

Hereinbelow, the present invention will be described in detail by way ofembodiments thereof illustrated in the accompanying drawings.

First Embodiment

FIG. 1 is a longitudinal sectional view showing an example of themain-part construction of a light emitting device according to a firstembodiment of the invention.

As shown in FIG. 1, the light emitting device 1 of this first embodimentincludes an LED (Light Emitting Diode) chip 6 mounted on a substrate 2.The LED chip 6 has an anode electrode (not shown) connected to aninterconnect pattern 5A formed on the substrate 2, and a cathodeelectrode (not shown) connected with a bonding wire 7 to anotherinterconnect pattern 5B formed on the substrate 2. The LED chip 6 is ablue LED chip having a primary emission peak in a blue wavelength rangeof 400 nm to 500 nm wavelengths as an example.

This light emitting device 1 also has a layered primer 10 that coversthe LED chip 6, the interconnect patterns 5A, 5B and the substrate 2.The light emitting device 1 further has a sealing resin portion 3 thatcovers the primer 10 in close contact with the primer 10 to provide aresin sealing of the LED chip 6. In this embodiment, unshown fluorophorand filler for wavelength conversion of light derived from the blue LEDchip 6 are added in the sealing resin portion 3. In this firstembodiment, an alumina substrate having high optical reflectance forvisible light was used as the substrate 2. The thickness of thissubstrate 2 was set to 0.3 mm as an example. The interconnect patterns5A, 5B formed on the surface of the substrate 2 were Ag interconnectpatterns. It is noted that these interconnect patterns 5A, 5B may alsobe made from Ag, or AgBi-based alloy, or AgNd-based alloy. Theinterconnect patterns 5A, 5B may also be made from an Ag alloycontaining 0.5 to 5.0 wt % of at least one kind of metal selected fromPt, Au, Cu, Pd, Mg, Ti and Ta.

Further, an external connection electrode 8A is formed on the bottomface side of the substrate 2, and the external connection electrode 8Ais electrically connected to the interconnect pattern 5A under the LEDchip 6 via a through conductive layer 9A provided so as to extendthrough the substrate 2 in its thicknesswise direction. Another externalconnection electrode 8B is also formed on the bottom face side of thesubstrate 2, and the external connection electrode 8B is electricallyconnected to the interconnect pattern 5B via a through conductive layer9B provided so as to extend through the substrate 2 in its thicknesswisedirection.

Also in this first embodiment, the primer 10 formed on the substrate 2so as to cover the LED chip 6, which is made from acrylic resin, isformed to a thickness of 1 μm by application onto the entire surface ofthe substrate 2 by spin coating process. The thickness of the primer 10is desirably set within a range of 0.01 μm to 100 μm.

The sealing resin portion 3 covering the primer 10, which is about 0.4mm thick, seals the LED chip 6 with resin. The sealing resin portion 3was provided, as an example, by adding silicone resin particles (notshown) having a mean particle size of 5 μm as a filler into dimethylsilicone resin.

In the sealing resin portion 3, an unshown fluorophor that convertswavelength of the light from the blue LED chip 6 to emit fluorescentlight is further added. In this first embodiment, as the fluorophor, ayellow fluorophor having a high luminous efficacy and a mean particlesize of 5 μm such as Eu:BOSE or ROSE (europium-activated strontiumbarium orthsilicate, (Ba.Sr)₂SiO₄:Eu) was used. This yellow fluorophorabsorbs blue light emitted from the blue LED chip 6 and emits yellowfluorescent light having an emission peak in a wavelength range of 550nm to 600 nm wavelengths.

A surface of the sealing resin portion 3, parallel to the surface of thesubstrate 2, is a generally flat surface. A side face of the lightemitting device 1 in this first embodiment is flat-surface shaped, wherethe sealing resin portion 3 and moreover the substrate 2 thereunder arecut vertical to the surface of the substrate 2, so that the lightemitting device 1 is formed into a rectangular parallelopiped shape, asa whole shape, which is thick in thickness and larger in an area inin-surface directions of the substrate 2. More specifically, the lightemitting device 1 has a thickness of 0.7 mm, a lateral width of 1.6 mmand a longitudinal width of 2.6 mm as an example. It is noted that thelateral width is a width in a direction parallel to the drawing sheet ofFIG. 1 and the longitudinal width is a width in a direction vertical tothe drawing sheet of FIG. 1.

In the first embodiment, the acrylic resin used as the primer 10 is amaterial which is, although as good as generally 100% at gas barrierproperty in comparison to dimethyl silicone resin of good lightresistance used for the sealing resin portion 3, yet cannot be regardedas so good at light resistance. For this reason, the primer 10 usingacrylic resin is discolored when subjected to long-time irradiation ofshort-wavelength, high-energy light such as blue light emitted from theblue LED chip 6, and this causes an optical loss. Therefore, it isdesirable that the primer 10 made from the acrylic resin is formed asthin as possible so as to minimize the optical loss.

As described above, applying the primer 10 by spin coating makes itpossible to provided a smaller thickness of the primer, yet depressionsand projections, if present on the surface of the substrate 2, cause theprimer 10 to be thicker at and near those depressions and projections.Therefore, the interconnect patterns 5A, 5B forming the interconnectlayer are desirably thinner in layer thickness than the primer 10. Also,the LED chip 6 is preferably one which does not need a bonding wire,such as flip chips, and besides it is desirable that the LED chip 6 hasa trapezoidal upper surface as an example so that the substrate surfacewith the LED chip 6 mounted thereon can be made more flattened.

In addition, the substrate 2 is desirably made from any one of opticallyreflective resin, metal and ceramic. In this case, since lightirradiated from the LED chip 6 is reflected by the substrate 2, thelight irradiated from the LED chip 6 can be prevented from attenuating.

Next, a method for producing the light emitting device 1 of the firstembodiment is explained in detail with reference to FIG. 1 and FIGS. 2Ato 2E. It is noted that FIGS. 2A to 2E are schematic sectional views forexplaining individual production steps of the production method for thelight emitting device 1 of the first embodiment.

First, FIG. 2A shows the substrate 2. Although not shown in FIG. 2A, theinterconnect patterns 5A, 5B, the blue LED chip 6 and the bonding wire 7shown in FIG. 1 are formed on the top face 2A side of the substrate 2.Also, the interconnect patterns 5A, 5B, the blue LED chip 6 and thebonding wire 7 are provided in plurality on the top face 2A of thesubstrate 2 longitudinally and laterally in an array. Also although notshown in FIG. 2A, the external connection electrodes 8A, 8B and thethrough conductive layers 9A, 9B electrically connected to the externalconnection electrodes 8A, 8B shown in FIG. 1 are formed on the bottomface 2B side of the substrate 2. It is noted that the interconnectpatterns 5A, 5B are designed as appropriate in accordance with the arraypattern or electrode formation of the LED chip 6. As described before,the interconnect pattern 5A is connected directly to the anode electrode(not shown) of the blue LED chip 6, and the cathode electrode of theblue LED chip 6 is connected to the interconnect pattern 5B by thebonding wire 7.

Next, as shown in FIG. 2B, a dam sheet 11 made of the silicone resin isaffixed to the substrate 2 on which the LED chip 6 and the bonding wire7 have been mounted. The dam sheet 11 made of silicone resin is for useof damming the primer 10 and the sealing resin portion 3. Thereafter, byair dispensation, the primer 10 is applied to the surface of thesubstrate 2, being allowed to dry. Appropriately diluting the primer 10allows the primer 10 to be reduced in thickness after its drying andafter the volatilization of the solvent.

In addition, the procedure may also be that the dam sheet 11 is affixedto the surface of the substrate 2 after the primer 10 is applied ontothe surface of the substrate 2 by spin coating process. In this case,the primer 10 can be applied onto the surface of the substrate moreuniformly and thinly, and moreover it becomes possible to preventformation of primer accumulation in recessed corner portions that formborder portions between the primer 10 and the dam sheet 11.

Next, the substrate 2 is set on a press machine including an unshownheating plate and, as shown in FIG. 2C, liquid silicone resin 3 a toform the sealing resin portion 3 is injected onto the surface of thesubstrate 2 by air dispensation. In this liquid silicone resin 3 a,unshown fluorophor and filler are added and stirred and defoamed by astirring and defoaming machine. In this case, the weight ratio of thefiller to the liquid silicone resin to the fluorophor was set to60:100:62 as an example.

Further, in FIG. 2D, a flat metal mold 12 is pressed onto the surface ofthe sealing resin 3 a to achieve a press. The metal mold 12 has afunction of serving as a lid of a mold container to flatten the surfaceof the sealing resin 3 a. Thereafter, the sealing resin 3 a is cured by10-minute heating and pressing at 100° C., by which the sealing resinportion 3 is formed.

Further, in FIG. 2E, dicing of the substrate 2 and the sealing resinportion 3 on the substrate 2 into a specified size so that individuallight emitting devices 1 are cut apart. This dicing is performed inaccordance with the above-described interconnect patterns. Through thesteps described above, the individual light emitting devices 1 dicedinto chips are formed.

As shown above, the production method for the light emitting device 1 ofthe first embodiment includes a step for applying the primer 10 to thesubstrate 2 on which the LED chip 6 as a light emitting element and thebonding wire 7 have been mounted, a step for mixing and stirring thesealing resin 3 a with fluorophor and filler added thereto, a step forcovering the surface 2A of the substrate 2, on which the LED chip 6 hasbeen mounted, with the sealing resin 3 a with fluorophor and filleradded thereto, a step for flattening and heating the surface by a pressto make the sealing resin material 3 a cured, and a dicing step forcutting apart individual light emitting devices 1.

The light emitting device 1 fabricated in this way was subjected to asulfuration accelerated test under 40° C., 80% RH, H₂S 3 ppm and 80-hourleaving conditions, after which almost no discoloration of the Aginterconnect patterns 5A, 5B was seen. On the other hand, a lightemitting device of a comparative example fabricated without applying theprimer 10 was discolored black by the sulfuration accelerated test. Asto a ratio based on an initial value, the light emitting device 1 ofthis embodiment resulted in an axial luminosity of 88%, while thecomparative example (with no primer) resulted in an axial luminosity of60%.

In addition, the primer 10 desirably has a thickness within a range of0.01 μm to 100 μm. The upper-limit value 100 μm of the thickness of theprimer 10 depends on a limit value of brightness lowering rate due tolight loss by discoloration-induced yellowing caused by heat and light,while the lower-limit value 0.01 μm depends on coating irregularitiesand an upper limit of gas permeation amount. This is applicable incommon to the following individual embodiments.

The primer 10 typified by acrylic resins is high in gas barrierproperty, particularly compared with dimethyl-based silicone resin. Onthe other hand, such primers as acrylic resins are, in general, inferiorin light resistance to the sealing resin portion 3. Therefore, combiningthe smaller-in-thickness primer 10 with the sealing resin portion 3makes it possible to provide a structure superior in both gas barrierproperty and light resistance.

According to the light emitting device 1 of the first embodiment,blackening of the interconnect patterns 5A, 5B formed of silver patternscan be prevented so that decreases of the reflectivity and decreases ofthe luminosity and chromaticity can be prevented. Also, according to theabove-described production process shown in FIGS. 2A to 2E, the processis the same as the conventional one except that the application anddrying step of the primer 10 is executed before the formation of thesealing resin portion 3, thus the production process being simple andcost-increase suppressed. Further, the primer 10 has a refractive indexgenerally equal to that of the sealing resin portion 3 (1.4 to 1.5 inboth cases), and is excellent in light transmissivity. It is noted thatthe refractive index of the sealing resin portion 3 and the refractiveindex of the primer 10 may be set generally equal to each other within arange of 1.2 to 1.8.

Second Embodiment

Next, a light emitting device 21 according to a second embodiment of theinvention is described with reference to FIG. 3A. FIG. 3A is alongitudinal sectional view showing a main-part construction of thelight emitting device 21.

As shown in FIG. 3A, in the light emitting device 21 of the secondembodiment, a first LED chip 26 is mounted on a first portion 25A of afirst lead frame 25 so that a lower electrode of the first LED chip 26is electrically connected to the first portion 25A. Also, a secondportion 25B of the first lead frame 25 is placed so as to be apart fromthe first portion 25A, and the second portion 25B is electricallyconnected to an upper electrode of the first LED chip 26 by a gold wire27. Further, the first, second portions 25A, 25B of the first lead frame25 are fixed by a resin portion 22 which surrounds the periphery of theLED chip 26 and which is formed by insert molding. The first portion 25Aof the first lead frame 25, which extends outward from the surface onwhich the LED chip 26 is mounted, is formed so as to surround one endportion 28 of a base portion 22A of the resin portion 22. That is, thefirst portion 25A is bent over a top face 22A-1, a side face 22A-2 and abottom face 22A-3 of the base portion 22A, by which an externalconnection terminal 31 to be electrically connected to a mount board orthe like is provided. The base portion 22A forms a base substrate. Also,the second portion 25B of the first lead frame 25 is similar in shape tothe first portion 25A. That is, the second portion 25B, which extendsoutward from the surface on which the LED chip 26 is mounted, is formedso as to surround the other end portion 29 of the base portion 22A. Thesecond portion 25B is bent over a top face 22A-4, a side face 22A-5 anda bottom face 22A-6 of the base portion 22A, by which an externalconnection terminal 32 to be electrically connected to a mount board orthe like is provided. The resin portion 22 has wall portions 22B, 22Bprotruding from both ends of the base portion 22A.

The first, second portions 25A, 25B of the first lead frame 25 may have,on their surfaces, a surface layer (not shown) for enhancing thereflectivity of light emitted from the LED chip 26, where the surfacelayer may be made from, for example, Ag or AgBi-based alloy, orAgNd-based alloy. Also, the surface layer may be made from an Ag alloycontaining 0.5 to 5.0 wt % of at least one kind of metal selected fromamong Pt, Au, Cu, Pd, Mg, Ti and Ta. With an Ag alloy used, the opticalreflectance, although somewhat lower than that of pure Ag, is yet even alittle improved in terms of deteriorations due to corrosive gas ormoisture. The surface layer, particularly with Ag used therefor, iscovered with the primer only within the LED chip mounting surface asdescribed later, thus providing deterioration countermeasures for thesurface layer. Therefore, the surface layer is preferably provided onlywithin the LED chip mounting surface, and desirably not formed atportions that extend along the side faces and the bottom faces of theresin portion 22 within the first, second portions 25A, 25B of the leadframe so as to be exposed outside.

In this second embodiment, in addition to the first LED chip 26 shown inFIG. 3A, second, third LED chips (not shown) are mounted on second,third lead frames (not shown), respectively, on a deeper side beyond thedrawing sheet of FIG. 3A. Anode electrodes and cathode electrodes ofthese second, third LED chips are connected to the second, third leadframes (not shown) formed on the base portion 22A of the resin portion22 independent of the first lead frame 25 on which the first LED chip 26is mounted. The first LED chip 26 is a blue LED chip having a primaryemission peak in a blue wavelength range of 400 nm to 500 nmwavelengths. The second LED chip is a green LED chip having a primaryemission peak in a green wavelength range of 480 nm to 580 nmwavelengths. The third LED chip is a red LED chip having a primaryemission peak in a red wavelength range of 600 nm to 700 nm wavelengths.

These first to third LED chips are coated with a layered primer 30.Further, a sealing resin portion 23 with silica and an anti-settlingadditive added thereto is formed so as to cover the top of the primer 30and come into close contact with the primer 30, so that the first tothird LED chips are resin-sealed by the sealing resin portion 23.

As the insert-molded resin portion 22, a white resin that reflects lightis preferably adoptable, and PPA (polyphthalamide) was adopted in thissecond embodiment. Whereas its use with high brightness may involve aphenomenon that the surface layer made from Ag or Ag alloy on thesurfaces of the first, second portions 25A, 25B reacts with moistureabsorbed by the sealing resin portion 23 so as to be blackened, thisblackening can also be prevented by the coating with the primer 30. Thethickness of the resin portion 22 was set to 1.4 mm. Also, the second,third lead frames, like the first lead frame 25, also extend from sidefaces 22A-1, 22A-2 to bottom faces 22A-3, 22A-6 of the base portion 22Ato form third external connection electrodes 31, 32.

As shown in FIG. 3A, a metal reflection coating 33 is formed by Agplating on an inner wall surface 22D of the wall portion 22B in theresin portion 22. The metal reflection coating 33 and the wall portion22B constitute a reflector. It is noted that the metal reflectioncoating 33 may also be made from Ag or AgBi-based alloy, or AgNd-basedalloy. The metal reflection coating 33 may also be made from an Ag alloycontaining 0.5 to 5.0 wt % of at least one kind of metal selected fromPt, Au, Cu, Pd, Mg, Ti and Ta.

Then, the primer 30 of silane-based resin is applied by air dispensationprocess at thicknesses of 1 to 10 μm so as to cover the metal reflectioncoating 33, the first to third lead frames, the first to third LED chipsand the base portion 22A.

In this second embodiment, the primer 30 is smallest in thickness asthin as 1 μm in the first portion 30A covering the metal reflectioncoating 33, largest in thickness as thick as 10 μm in the second portion30B on the interconnect pattern, and 4 μm thick at the third portion 30Con the base portion 22A. The sealing resin portion 23 covering theprimer 30 is 0.7 mm thick. In the sealing resin portion 23, silica andan anti-settling additive having a mean particle size of 5 μm are addedinto the silicone resin.

The light emitting device 21 of this second embodiment has sizes of athickness of 1.4 mm, a lateral width of 3.2 mm and a longitudinal widthof 2.8 mm. It is noted that the lateral width means a width in adirection parallel to the drawing sheet in FIG. 3A, and the longitudinalwidth means a width in a direction vertical to the drawing sheet in FIG.3A.

In addition, in the second embodiment, the metal reflection coating 33formed on the inner wall surface 22D of the wall portion 22B in theresin portion 22 may be omitted.

In this second embodiment, combining the thin primer 30 with the sealingresin portion 23 makes it possible to provide a structure superior inboth gas barrier property and light resistance. As a result of this,blackening of the interconnect patterns formed of silver patterns andthe metal reflection coating 33 can be prevented so that decreases ofthe reflectivity and decreases of the luminosity and chromaticity can beprevented. Also, in this second embodiment, the fabrication process canbe achieved by the same process as the conventional one except that theapplication and drying step of the primer 30 is executed before theformation step of the sealing resin portion 23, thus the productionprocess being simple and cost-increase suppressed. Further, the primer30 has a refractive index generally equal to that of the sealing resinportion 23 (1.4 to 1.5 in both cases), and decreases of light extractionefficiency can be suppressed without occurrence of refraction orscattering at the interface between the primer 30 and the sealing resinportion 23. Also, since the primer 30 is applied also on the surface ofthe base portion 22A of the resin portion 22 and the metal reflectioncoating 33, close contact between the resin portion 22 or the metalreflection coating 33 and the sealing resin portion 23 can be enhanced.

Next, a modification of the second embodiment is described withreference to FIG. 3B. This modification differs from the secondembodiment in that a primer 35 which covers not only places covered withthe primer 30 in FIG. 3A but also the side faces of the resin portion 22and the first to third lead frame portions formed along the side facesis included instead of the primer 30 of FIG. 3A. Besides, thismodification differs from the second embodiment in that no metalreflection coating 33 is formed on the wall surface 22D of the wallportion 22B in the resin portion 22.

In a light emitting device 21A of this modification, the primer 35 isformed by dip coating on surfaces of the resin portion 22, the first tothird LED chips and the first to third lead frames. As shown in FIG. 3B,the primer 35 covers not only the inner wall surface 22D but also anouter wall surface 22E of the wall portion 22B of the resin portion 22,and further covers the side portions 25A-1, 25B-1 of the first leadframe 25 and side portions of the second, third lead frames.

Desirably, the primer 35 serves as coating of all the portions where themetal surface is exposed on the surface except the external connectionelectrodes 31, 32 that form mounting surfaces of the first, secondportions 25A, 25B of the first lead frame 25 as well as except theexternal connection electrodes (not shown) that form mounting surfacesof the second, third lead frames.

The light emitting device 21A of this modification has side lightemitting LEDs as the first to third LED chips, and has sizes of athickness of 1.2 mm, a lateral width of 3.8 mm and a longitudinal widthof 0.6 mm.

In this modification, since a narrow recess portion U is between thewall portion 22B of the resin portion 22 and the first to third LEDchips, coating of the primer 35 was fulfilled by dipping process. In thecoating by dipping process, the primer 35 tends to vary in thickness,and therefore a difference between the refractive index of the primer 35and the refractive index of the sealing resin portion 23 causes thelight scattering lost to increase. Accordingly, in the case of thismodification, it is desirable that the refractive index of the primer 35and the refractive index of the sealing resin portion 23 are, inparticular, of an equivalent level.

Also, as shown in FIG. 3B, preferably, the sealing resin portion 23 isformed so as to be in close contact with the surface of at least part ofthe primer 35. Particularly, when there is a side face surrounding theperiphery of the primer 35 (inner wall surface 22D of wall portion 22B)as shown in FIGS. 3A and 3B, it is preferable to form first the primer35 and then the sealing resin portion 23. In the case where the primer35 is formed on the sealing resin portion 23 conversely, when gascontained in the sealing resin portion 23 is bled out, there is noescape place sideways from within the light emitting device (package) 1so that the gas is inevitably directed upward, causing a possibilitythat the primer 35 may be damaged. Thus, it is preferable to form theprimer 35 before forming the sealing resin portion 23.

Third Embodiment

FIG. 4A is a longitudinal sectional view showing a main-partconstruction of a light emitting device according to a third embodimentof the invention.

As shown in FIG. 4A, in the light emitting device of the thirdembodiment, an LED chip 46 is mounted on a first portion 45A of a leadframe 45 so that a lower electrode of the LED chip 46 is electricallyconnected to the first portion 45A. The LED chip 46 is a blue LED chiphaving a primary emission peak in a blue wavelength range of 400 nm to500 nm wavelengths. Also, a second portion 45B of the lead frame 45 isplaced so as to be apart from the first portion 45A, and the secondportion 45B is electrically connected to an upper electrode of the LEDchip 46 by a gold wire 47. Further, the first, second portions 45A, 45Bof the lead frame 45 are fixed by a resin portion 42 which surrounds theperiphery of the LED chip 46 and which is formed by insert molding. Thefirst portion 45A of the lead frame 45, which extends outward from thesurface on which the LED chip 46 is mounted, is formed so as to surroundone end portion 48 of a base portion 42A of the resin portion 42. Thatis, the first portion 45A is bent over a top face 42A-1, a side face42A-2 and a bottom face 42A-3 of the base portion 42A, by which anexternal connection terminal 51 to be electrically connected to a mountboard or the like is provided. The base portion 42A forms a basesubstrate. Also, the second portion 45B of the lead frame 45 is similarin shape to the first portion 45A. That is, the second portion 45B,which extends outward from the surface on which the LED chip 46 ismounted, is formed so as to surround the other end portion 49 of thebase portion 42A. The second portion 45B is bent over a top face 42A-4,a side face 42A-5 and a bottom face 42A-6 of the base portion 42A, bywhich an external connection terminal 52 to be electrically connected toa mount board or the like is provided. The resin portion 42 has wallportions 42B, 42B protruding from both ends of the base portion 42A.

The first, second portions 45A, 45B of the lead frame 45 may have, ontheir surfaces, a surface layer (not shown) for enhancing thereflectivity of light emitted from the LED chip 46, where the surfacelayer may be made from, for example, Ag or AgBi-based alloy, orAgNd-based alloy. Also, the surface layer may be made from an Ag alloycontaining 0.5 to 5.0 wt % of at least one kind of metal selected fromamong Pt, Au, Cu, Pd, Mg, Ti and Ta. With an Ag alloy used, the opticalreflectance, although somewhat lower than that of pure Ag, is yet even alittle improved in terms of deteriorations due to corrosive gas ormoisture. The surface layer, particularly with Ag used therefor, iscovered with the primer only within the LED chip mounting surface asdescribed later, thus providing deterioration countermeasures for thesurface layer. Therefore, the surface layer is preferably provided onlywithin the LED chip mounting surface, and desirably not formed atportions that extend along the side faces and the bottom faces of theresin portion 42 within the first, second portions 45A, 45B of the leadframe 45 so as to be exposed outside.

In this third embodiment, a layered primer 40 is applied on the first,second portions 45A, 45B of the lead frame 45 and the base portion 42Aof the resin portion 42. Also, a sealing resin portion 43 is formed soas to cover the primer 40, the LED chip 46 and the inner wall surface ofthe wall portion 42B. This sealing resin portion 43 is in close contactwith the surface of the primer 40. The sealing resin portion 43 is madefrom a sealing resin to which added is a fluorophor (not shown) thatperforms wavelength conversion of light derived from the blue LED chip46.

As the insert-molded resin portion 42, a white resin that reflects lightis preferably adoptable, and PPA (polyphthalamide) was adopted in thisthird embodiment. Whereas its use with high brightness may involve aphenomenon that the surface layer made from Ag or Ag alloy on thesurfaces of the first, second portions 45A, 45B reacts with moistureabsorbed by the sealing resin portion so as to be blackened, thisblackening can also be prevented by the coating with the primer 40. Thethickness of the resin portion 42 was set to 1.4 mm.

In this third embodiment, the primer 40 is formed by applying and dryingan acrylic modified resin by dispensing process to a mean thickness of 2μm. Also, the primer 40 is formed with selected dispensing places so asto cover surfaces exposed to around the direct mounting portion for theblue LED chip 46 of the first portion 45A, but not to cover the LED chip46, and to cover the base portion 42A exposed from the first, secondportions 45A, 45B. Further, the sealing resin portion 43 that covers theprimer 40, the LED chip 46 and the wall portion 42B is formed at athickness of 0.4 mm.

In this sealing resin portion 43, a fluorophor (not shown) that performswavelength conversion of light derived from the blue LED chip 46 to emitfluorescent light is added in a silicone resin. In this thirdembodiment, as an example of the fluorophor, a yellow fluorophor havinga high luminous efficacy and a mean particle size of 6 μm such as Ce:YAG(cerium-activated yttrium-aluminum-garnet) was used. This yellowfluorophor absorbs blue light emitted from the blue LED chip 46 andemits yellow fluorescent light having an emission peak in a wavelengthrange of 550 nm to 600 nm wavelengths. Also, a surface of the sealingresin portion 43, parallel to the surface of the base portion 42Aforming the substrate, is a generally flat surface. More specifically,the light emitting device of this third embodiment has a thickness of1.5 mm, a lateral width of 5.0 mm and a longitudinal width of 5.0 mm asan example.

Next, FIG. 4B shows a modification of the third embodiment. Thismodification differs from the third embodiment in that a metalreflection coating 44 by Ag plating is formed on the inner wall surfaceof the wall portion 42B of the resin portion 42 and that a primer 55which covers this metal reflection coating 44 is included. The metalreflection coating 44 and the wall portion 42B constitute a reflector.It is noted that the metal reflection coating 44 may be made from Ag orAgBi-based alloy, or A Nd-based alloy. The metal reflection coating 44may also be made from an Ag alloy containing 0.5 to 5.0 wt % of at leastone kind of metal selected from Pt, Au, Cu, Pd, Mg, Ti and Ta.

The primer 55, like the above-described primer 40, is formed withselected dispensing places so as to cover surfaces exposed to around thedirect mounting portion for the blue LED chip 46 of the first portion45A of the lead frame 45, but not to cover the LED chip 46, and to coverthe base portion 42A of the resin portion 42 exposed from the firstportion 45A and the second portion 45B of the lead frame 45.

In this modification, primer coating may be done independently for thesurface portions of the first portion 45A other than chip mountingportion and for the inner wall surface of the wall portion 42B formingthe reflector, during the formation process of the primer 55. In thiscase, there is an advantage that the primer 55 can easily be madeuniform in thickness among individual places.

In the third embodiment and its modification, combining the thin primer55 with the sealing resin portion 43 makes it possible to provide astructure superior in both gas barrier property and heat resistance. Asa result of this, blackening of silver patterns forming the first,second portions 45A, 45B of the lead frame 45 and the metal reflectioncoating 44 can be prevented so that decreases of the reflectivity anddecreases of the luminosity and chromaticity can be prevented. Also, thefabrication process can be achieved by the same process as theconventional one except that the application and drying step of theprimer 40, 55 is executed before the formation step of the sealing resinportion 43, thus the production process being simple and cost-increasesuppressed. Further, since the primer 40, 55 does not cover the LED chip46, there occurs neither attenuation nor confusion of light, andmoreover discoloration of the primer 40, 55 due to heat generation ofthe LED chip 46 can be prevented. Besides, the primer 40, 55 has arefractive index generally equal to that of the sealing resin portion 43(1.4 to 1.5 in both cases), being excellent in light transmissivity.Also, since the primer 40, 55 is applied also on the surface of the baseportion 42A of the resin portion 42 and the metal reflection coating 44,close contact between the resin portion 42 or the metal reflectioncoating 44 and the sealing resin portion 43 can be enhanced.

Preferably, as shown in FIGS. 4A and 4B, the sealing resin portion 43 isformed so as to be in close contact with the surface of at least part ofthe primer 40, 55. Particularly, when there is a side face surroundingthe periphery of the primer 40, 55 (inner wall surface of wall portion42B) as shown in FIGS. 4A and 4B, it is preferable to form first theprimer 40, 55 and then the sealing resin portion 43. Meanwhile, in thecase where the primer 40, 55 is formed on the sealing resin portion 43,when gas contained in the sealing resin portion 43 is bled out, there isno escape place sideways from within the light emitting device (package)so that the gas is inevitably directed upward, causing a possibilitythat the primer 40, 55 may be damaged. Thus, it is preferable to formthe primer 40, 55 before forming the sealing resin portion 43.

Fourth Embodiment

Next, a light emitting device according to a fourth embodiment of theinvention is described with reference to FIG. 5A. FIG. 5A is alongitudinal sectional view showing a main-part construction of thelight emitting device according to the fourth embodiment.

In the light emitting device of this fourth embodiment, as shown in FIG.5A, interconnect patterns 65A-65D are formed on a substrate 62. It isnoted that the interconnect patterns 65A-65D may be made from Ag orAgBi-based alloy, or AgNd-based alloy. The interconnect patterns 65A-65Dmay also be made from an Ag alloy containing 0.5 to 5.0 wt % of at leastone kind of metal selected from Pt, Au, Cu, Pd, Mg, Ti and Ta.

Then, a layered primer 70 is applied on the interconnect patterns65A-65D and the surface of the substrate 62 exposed from theinterconnect patterns 65A-65D by dipping process. Blue LED chips 66, 67,68 having a primary emission peak in a blue wavelength range of 400 nmto 500 nm wavelengths are mounted on the primer 70. Further, a sealingresin portion 63 is formed so as to cover these blue LED chips 66-68 andthe primer 70. In this sealing resin portion 63, a fluorophor (notshown) that performs wavelength conversion of light derived from theblue LED chips 66-68 is added.

In this fourth embodiment, a 96%-alumina substrate having a high opticalreflectance for visible light was used as the substrate 62. A thicknessof the substrate 62 was set to 1.5 mm. Also, the interconnect patterns65A-65D formed on the surface of the substrate 62 are made fromAu/Ni/AgPd. The primer 70 is a 5 μm-thick urethane resin-based primerapplied on the entire top surface of the substrate 62 including theinterconnect patterns 65A-65D.

The blue LED chip 66 is mounted on the primer 70 between the anode-sideinterconnect pattern 65B and the cathode-side interconnect pattern 65Avia a die-bond paste. In this blue LED chip 66, its anode-side electrodeis connected to the anode-side interconnect pattern 65B by a gold wire76B, and its cathode-side electrode is connected to the cathode-sideinterconnect pattern 65A by a gold wire 76A.

Also, the blue LED chip 67 is mounted on the primer 70 between theanode-side interconnect pattern 65B and the cathode-side interconnectpattern 65C via a die-bond paste. In this blue LED chip 67, itsanode-side electrode is connected to the anode-side interconnect pattern65B by a gold wire 77A, and its cathode-side electrode is connected tothe cathode-side interconnect pattern 65C by a gold wire 77B.

Also, the blue LED chip 68 is mounted on the primer 70 between theanode-side interconnect pattern 65D and the cathode-side interconnectpattern 65C via a die-bond paste. In this blue LED chip 68, itsanode-side electrode is connected to the anode-side interconnect pattern65D by a gold wire 78B, and its cathode-side electrode is connected tothe cathode-side interconnect pattern 65C by a gold wire 78A.

In this embodiment, those three blue LED chips 66-68 are arranged andconnected in series. In this embodiment also, 11 LED chips (not shown)similar to the LED chip 66 are arrayed and connected in parallel on thedepth side of the drawing sheet of FIG. 5A. Also, 11 LED chips (notshown) similar to the LED chip 67 are arrayed and connected in parallelon the depth side of the drawing sheet of FIG. 5A. Also, 11 LED chips(not shown) similar to the LED chip 68 are arrayed and connected inparallel on the depth side of the drawing sheet of FIG. 5A.

In this embodiment, those individual LED chips including the LED chips66-68 are subjected to die bonding and wire bonding in a state in whichthe primer 70 has been formed. Also, in FIG. 5A, both-end interconnectpatterns 65A, 65D extend to form external connection electrodes.

The mounting of the individual LED chips including the LED chips 66-68is performed via die-bond paste as described above. However, the primer70 may be used instead of the die-bond paste in the case where viscosityand adhesion of the primer 70 are tuned as required and the LED chipsare mounted on the substrate 62 before the curing of the primer 70.

A sealing resin portion 63 is formed so as to provide a 0.4 mm thickresin sealing of methylsilicone resin on the LED chips and the primer70. This sealing resin portion 63 can be fabricated by injecting andcuring the sealing resin onto the substrate 62 with a dam sheet (notshown) made of Teflon (registered trademark), and then removing the damsheet. In the silicone resin that forms the sealing resin portion 63, afluorophor (not shown) that performs wavelength conversion of lightderived from the blue LED chips 66-68 to emit fluorescent light isadded. The sealing resin portion 63 is in close contact with the primer70.

Also in this fourth embodiment, particles of the fluorophor include ared fluorophor made of europium-activated pure nitride fluorophor((Sr.Ca)AlSiN₃:Eu) having a mean particle size of 5 μm, and a greenfluorophor made of a europium-activated fluorophor ((Si.Al)₆(O.N)₈:Eu).The red fluorophor performs wavelength conversion of light derived fromthe blue LED chips 66-68 to emit red fluorescent light having anemission peak in a wavelength range of 600 nm to 750 nm wavelengths.Also, the green fluorophor emits green fluorescent light having anemission peak in a wavelength range of 490 nm to 600 nm wavelengths.

A surface of the sealing resin portion 63, parallel to the surface ofthe substrate 62, is a generally flat surface. More specifically, thelight emitting device of this fourth embodiment has a thickness of 1.5mm, a lateral width of 18.0 mm and a longitudinal width of 18.0 mm as anexample.

Next, a modification of the fourth embodiment is shown in FIG. 5B. Inthis modification, a metal reflection coating 73 by Ag plating is formedon a surface of the substrate 62. It is noted that the metal reflectioncoating 73 may be made from Ag or AgBi-based alloy, or AgNd-based alloy.The metal reflection coating 73 may also be made from an Ag alloycontaining 0.5 to 5.0 wt % of at least one kind of metal selected fromPt, Au, Cu, Pd, Mg, Ti and Ta.

Then, a primer 78 is applied at a thickness of 60 μm so as to cover themetal reflection coating 73. Further, Au/Ni/W interconnect patterns 75A,75B, 75C, 75D are formed on the primer 78. The primer 78 functions as aninsulating layer between the metal reflection coating 73 and theindividual interconnect patterns 75A-75D.

The blue LED chip 66 is mounted on the primer 78 between the anode-sideinterconnect pattern 75B and the cathode-side interconnect pattern 75Avia a die-bond paste. In this blue LED chip 66, its anode-side electrodeis connected to the anode-side interconnect pattern 75B by a gold wire76B, and its cathode-side electrode is connected to the cathode-sideinterconnect pattern 75A by a gold wire 76A.

Also, the blue LED chip 67 is mounted on the primer 78 between theanode-side interconnect pattern 75B and the cathode-side interconnectpattern 75C via a die-bond paste. In this blue LED chip 67, itsanode-side electrode is connected to the anode-side interconnect pattern75B by a gold wire 77A, and its cathode-side electrode is connected tothe cathode-side interconnect pattern 75C by a gold wire 77B.

Also, the blue LED chip 68 is mounted on the primer 78 between theanode-side interconnect pattern 75D and the cathode-side interconnectpattern 75C via a die-bond paste. In this blue LED chip 68, itsanode-side electrode is connected to the anode-side interconnect pattern75D by a gold wire 78B, and its cathode-side electrode is connected tothe cathode-side interconnect pattern 75C by a gold wire 78A.

In this modification, a sealing resin portion 79 formed in the samemanner as the sealing resin portion 63 of the above-described fourthembodiment is included. In FIG. 5B, both-end interconnect patterns 75A,75D extend to form external connection electrodes. Also in thismodification, the primer 78 may cover not only the upper surface of thesubstrate 62 but its entire surface.

In the fourth embodiment and its modification, combining the thin primer70, 78 with the sealing resin portion 63, 79 makes it possible toprovide a structure superior in both gas barrier property and heatresistance. As a result of this, corrosion of AgPd that is the basis ofthe interconnect pattern 65A-65D, 75A-75D, or Ag of the metal reflectioncoating 73 portion, can be prevented so that decreases of thereliability and decreases of the luminosity and chromaticity can beprevented. Also, in the fourth embodiment and the modification, thefabrication process can be achieved by the same process as theconventional one except that the application and drying step of theprimer 70, 78 is executed before the die-bonding step or theinterconnect pattern formation step, thus the production process beingsimple and cost-increase suppressed. Besides, the primer 70, 78 has arefractive index generally equal to that of the sealing resin portion63, 79 (1.4 to 1.5 in both cases), being excellent in lighttransmissivity. Further, since the primer 70, 78 is not applied on thetop surfaces of the individual LED chips, there occurs neitherattenuation nor confusion of light, so that stable characteristics canbe obtained.

Fifth Embodiment

Next, a light emitting device according to a fifth embodiment of theinvention is described with reference to FIG. 6. FIG. 6 is alongitudinal sectional view showing a main-part construction example ofthe light emitting device according to the fifth embodiment.

As shown in FIG. 6, a plurality of light emitting units 81 mounted on asubstrate 82 are included in the light emitting device of this fifthembodiment. The light emitting units 81 are sealed with resin at athickness of 0.3 mm by a resin sealing portion formed on a 0.3 mm thickalumina substrate.

Each light emitting unit 81 has a blue LED chip having a primaryemission peak in a blue wavelength range of 400 nm to 500 nmwavelengths. This blue LED chip 86 is mounted on the substrate 82. Asshown in FIG. 6, an 0.5 μm thick epoxy resin-based primer 90 is appliedover regions of the top surface of the substrate 82 other than itsregions over which the LED chip 86 is mounted.

Also, a reflector member 93 is attached onto the primer 90 so as tosurround each LED chip 86. This reflector member 93 has an Ag-platedreflecting surface 93A, and peripheries of the reflecting surface 93Aare dip coated with a primer 94 of acrylic resin beforehand. Also, asealing resin portion 83 is formed so as to cover the reflector member93, the primer 90 and the LED chip 86. The sealing resin portion 83 ismade from a sealing resin with a fluorophor added thereto, and servesfor resin sealing of the LED chip 86. It is noted that the fluorophormay be one which emits light yellow. Further, it is also possible thatthe sealing resin does not contain any fluorophor and a combination ofLED chips for individual RGB (Red, Green, Blue) colors and a sealingresin portion containing no fluorophor is adopted.

In this fifth embodiment, a glass epoxy printed board was used as thesubstrate 82. A thickness of the substrate 82 was set to 1.0 mm. Also,unshown Cu interconnect patterns are formed on the surface of thesubstrate 82. The light emitting units 81 are mounted on the Cuinterconnect patterns. The sealing resin portion 83 may also belens-shaped. Further, the above-described reflector member 93 may alsobe given by a metal block having a Ag-plated surface.

In this fifth embodiment, combining the thin primer 90 with the sealingresin portion 83 makes it possible to provide a structure superior inboth gas barrier property and heat resistance. As a result of this, Cublackening of the Cu interconnect patterns (not shown) can be preventedso that decreases of the reliability and decreases of the luminosity andchromaticity can be prevented. Also, in the fifth embodiment, theproduction process can be achieved by a simple, cost-increase suppressedprocess because the primer 90 is applied on the entire surface of thesubstrate 82 other than the mounting portion of the LED chip 86.

Also in this fifth embodiment, since the primer is applied on the entiresurface of the substrate 82 around the LED chips, the gas barrierproperty (halogen resistance) of the substrate as a whole can beenhanced. Therefore, the light emitting device can be suitably used asLED devices for vehicle and backlight use. Also, primer coating for thereflector members 93 of the individual light emitting units 81 isperformed independently and separately, there is an advantage that theprimer can easily be made uniform in thickness among the individualreflector members 93. Besides, the primer 90, 94 has a refractive indexgenerally equal to that of the sealing resin portion 83 (1.4 to 1.5 inboth cases), being excellent in light transmissivity. Further, since theprimer is not applied on the sealing resin portion 83, light istransmitted therethrough without incurring attenuation or confusion oflight, eliminating a fear for explosion of gas contained in the sealingresin portion.

In addition, in the first to fifth embodiments, it is desirable that thecoefficient of thermal expansion of the sealing resin portion and thecoefficient of thermal expansion of the primer are generally equal toeach other. In this case, impairment of close contact between thesealing resin and the primer due to heat can be avoided.

REFERENCE SIGNS LIST

-   1, 21 . . . light emitting device-   2, 62, 82 . . . substrate-   3, 23, 43, 63, 79, 83 . . . sealing resin portion-   3 a . . . liquid silicone resin-   5A, 5B, 25A, 65A-65D, 75A-75D . . . interconnect pattern-   6, 26, 46, 66-68, 86 . . . LED chip-   7, 27, 47, 76A, 76B, 77A, 77B . . . bonding wire-   8A, 8B . . . external connection electrode-   31, 32, 51, 52 . . . external connection terminal-   9A, 9B . . . through conductive layer-   10, 30, 35, 55, 70, 78, 90, 94 . . . primer-   11 . . . dam sheet-   12 . . . metal mold-   22, 42 . . . resin portion-   22A, 42A . . . base portion-   22B, 42B . . . wall portion-   25, 45 . . . lead frame-   25A, 45A . . . first portion-   25B, 45B . . . second portion-   33, 44, 73 . . . metal reflection coating-   81 . . . light emitting unit-   93 . . . reflector member-   93A . . . reflecting surface

1. A light emitting device comprising: a substrate; a metal portionformed on a surface of the substrate; an LED chip mounted on thesubstrate; a primer made of resin which covers at least part of themetal portion; and a sealing resin portion which covers the LED chip andat least part of the primer to seal the LED chip, wherein the primer ismade from a resin which is higher in gas barrier property than thesealing resin portion.
 2. The light emitting device as claimed in claim1, wherein the primer is formed into a layer shape.
 3. The lightemitting device as claimed in claim 1, wherein the primer is made froman acrylic resin.
 4. The light emitting device as claimed in claim 1,wherein the metal portion includes an interconnect pattern.
 5. The lightemitting device as claimed in claim 1, wherein the metal portionincludes a lead frame.
 6. The light emitting device as claimed in claim1, wherein the metal portion includes a metal reflection coating.
 7. Thelight emitting device as claimed in claim 4, wherein a surface of themetal portion is made from Ag, or AgBi-based alloy, or AgNd-based alloy,or an Ag alloy containing 0.5 to 5.0 wt % of at least one kind of metalselected from Pt, Au, Cu, Pd, Mg, Ti and Ta.
 8. The light emittingdevice as claimed in claim 1, wherein the substrate is made from any oneof a light-reflective resin, metal and ceramic.
 9. The light emittingdevice as claimed in claim 1, wherein at least a top face of the LEDchip is exposed from the primer made of resin.
 10. The light emittingdevice as claimed in claim 1, wherein the LED chip has its top face andside face coated with the primer made of resin.
 11. The light emittingdevice as claimed in claim 1, wherein the primer covers a top face ofthe substrate.
 12. The light emitting device as claimed in claim 1,wherein the primer covers an entire surface of the substrate.
 13. Thelight emitting device as claimed in claim 1, wherein the primer covers atop face of the substrate, and the LED chip is mounted on the primercovering the top face of the substrate.
 14. The light emitting device asclaimed in claim 6, wherein the metal reflection coating is formed onthe substrate, the primer is formed on the metal reflection coating, andthe interconnect pattern is formed on the primer.
 15. The light emittingdevice as claimed in claim 1, wherein the primer has a thickness of 0.01μm to 100 μm.
 16. The light emitting device as claimed in claim 1,wherein the sealing resin portion is in close contact with a surface ofat least part of the primer.
 17. The light emitting device as claimed inclaim 1, wherein the LED chip is placed within a recess portion of thesubstrate, the primer covers a bottom face of the recess portion of thesubstrate, the sealing resin portion is in close contact with thesurface of the primer and seals the LED chip, and the primer is notexposed.
 18. The light emitting device as claimed in claim 1, whereinthe sealing resin portion is made from silicone resin.
 19. The lightemitting device as claimed in claim 1, wherein the sealing resin portioncontains a fluorophor.
 20. The light emitting device as claimed in claim1, wherein a refractive index of the sealing resin portion and arefractive index of the primer, both being within a range of 1.2 to 1.8,are generally equal to each other.
 21. The light emitting device asclaimed in claim 1, further comprising a reflector which is placedaround the LED chip and which reflects light emitted by the LED chip.22. The light emitting device as claimed in claim 21, wherein thereflector and the substrate are made from one identical base material.23. The light emitting device as claimed in claim 21, wherein a surfaceof the reflector is made from Ag, or AgBi-based alloy, or AgNd-basedalloy, or an Ag alloy containing 0.5 to 5.0 wt % of at least one kind ofmetal selected from Pt, Au, Cu, Pd, Mg, Ti and Ta.
 24. The lightemitting device as claimed in claim 21, wherein the primer covers thesurface of the reflector.
 25. The light emitting device as claimed inclaim 1, wherein a coefficient of thermal expansion of the sealing resinportion and a coefficient of thermal expansion of the primer aregenerally equal to each other.
 26. A method for producing the lightemitting device as claimed in claim 24, comprising the step of: applyingthe primer onto the surface of the reflector before placing thereflector around the LED chip.
 27. A method for producing the lightemitting device, comprising the steps of: applying a resin-made primeronto a substrate in which a metal portion is formed on its surface andon which an LED chip is mounted so that the resin-made primer covers atleast part of the metal portion; and coating the LED chip and at leastpart of the resin-made primer with a sealing resin and curing thesealing resin, thereby forming a sealing resin portion, wherein theprimer is made from a resin higher in gas barrier property than thesealing resin portion.
 28. A method for mounting the light emittingdevice as claimed in claim 1 onto a printed board onto which a primermade from a resin material identical to that of the primer has beenapplied.